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Biomedical subjects

A Briggs

Publications and source records attributed to A Briggs.

46 records · Page 3Linked to original sources
PubMed1978

Interaction of hydralazine and hydrazone derivatives with contractile mechanisms in rabbit aortic smooth muscle.

The mechanism of action and relative potency of hydralazine (H) and tow hydrazone derivatives were investigated using isolated rabbit aortic strips. H, hydralazine acetone hydrazone (HA) and hydralazine butanone hydrazone (HBH) relaxed established K+ and norepinephrine (NE) contractures, and inhibited the development of contractures to these two agents on preincubation. H, HA and HBH increased the threshold to Ca++ and decreased the maximum tension responses during K+-Ca++-contractures (HA greater than H, P less than .05; HBH greater than H P less than .01). The Ca++-dependent and Ca++-independent components of NE contractures were both inhibited by H, HA and HBH. NE contractures were more sensitive to the effects of H than K+ contractures. These results are consistent with the conclusion that H and hydrazone derivatives produce effects on vascular muscle both by interactions with the fluxes of Ca++ from the extracellular space and effects on release from cell stores. However, other possibilities need to be assessed experimentally.

Animals↗
PubMed1976

A new freeze-drying technique for processing biological materials.

Wet granulation and dry blending are standard techniques used in tablet formulation. Both techniques impose limitations on the ability to produce homogeneous tablets with rapid dissolution and controllability of the matrix for active ingredients. This report describes the development and application of a new freeze-system using a swirling bath of Freon-12 to process sensitive biological materials. The frozen beads produced with this process are subsequently freeze-dried and may be used to produce precise tablets. The ultra rapid freezing (7-14 milliseconds) provided by the Freon-12 process yiels amorphous homogeneous spheres by retarding component migration which permits precise control of pH and redox potential in the final product. Dissolution of tablets prepared by this Du Pont process is so rapid (8-12 seconds) that a special testing technique is required for measurement of dissolution time. Improved recoveries of activity have been demonstrated for sensitive biological materials compared to conventional freeze-drying. The optimization of droplet sizes is controlled by injection rate, stream diameter and surface velocity of the Freon-12 bath. Droplet size control permits attainment of weight precision in the range of 0.6 +/- 0.06% for a final 50 mg tablet. This compares with a tablet weight precision of 1% to 2% typical of dry blending and wet granulating. Potential applications of this technology include pharmaceuticals and the production of ultra precise reagent tablets for the Du Pont Automatic Clinical Analyser.

Biological Products↗
PubMed1974

Health and education.

Explore the source record for details and available documents.

Comprehensive Health Care↗
PubMedDate not supplied

Trying to do better than average: a commentary on 'statistical inference for cost-effectiveness ratios'.

In a recent paper, Laska, Meisner and Siegel address issues concerning hypothesis testing in cost-effectiveness analysis. They relate the relative magnitude of two average cost-effectiveness ratios to the incremental cost-effectiveness ratio and go on to propose a statistical procedure for testing the equality of two average ratios. In this paper, we show why the use of average cost-effectiveness ratios is misleading and argue that the appropriate focus for cost-effectiveness analysis is the estimation of confidence intervals around incremental cost-effectiveness ratios.

Confidence Intervals↗
PubMedDate not supplied

Uncertainty in the economic evaluation of health care technologies: the role of sensitivity analysis.

Given the increased use of economic evaluation to inform decision making in the health service, it is particularly important that the research methods used are critically assessed and, where possible, improved. The systematic handling of uncertainty in economic evaluation is an important area that remains methodologically underdeveloped. With the increased use of the clinical trial as a vehicle for economic evaluation, there has been recent interest in how the statistical methods routinely employed to handle uncertainty in clinical research might be applied to economic evaluation. This paper reviews the types of uncertainty that exist in economic evaluation and argues that some forms of uncertainty are not amenable to statistical methods. Sensitivity analysis is not a single approach but can take a number of different forms. The different types of sensitivity analysis are reviewed, with an indication of their strengths and weaknesses in relation to the different types of uncertainty in economic evaluation.

Cost-Benefit Analysis↗
PubMedDate not supplied

Sensitivity analysis in economic evaluation: a review of published studies.

A structured methodological review of journal articles published in 1992 was undertaken to determine whether recently published economic evaluation studies deal systematically and comprehensively with uncertainty. Ninety three journal articles were identified from a range of searches including a computerised search of the MEDLINE CD-Rom database. Articles were reviewed to determine how they had handled uncertainty in: a) data sources; b) generalisability; c) extrapolation; and d) analytic method. Articles were subsequently assessed to determine how they had represented this uncertainty in terms of the overall results of their analysis. Finally, studies were rated on the basis of their overall performance with respect to dealing systematically and comprehensively with uncertainty. Despite the numerous books and articles devoted to the appropriate methods to be employed by analysts conducting economic evaluation, 22 (24%) studies failed to consider uncertainty at all and 35 (38%) studies employed sensitivity analysis in a manner judged as inadequate. In all, 36 (39%) studies were judged to have given at least an adequate account of uncertainty with 13 (14%) of those judged to have provided a good account of uncertainty. Such disappointing results may reflect a general lack of detail in much of the methods literature concerning how sensitivity analysis should be applied and how results should be presented. Journal editors and readers of economic evaluation articles should acquaint themselves with the methods for handling uncertainty in order that they can critically evaluate the extent to which authors have allowed for uncertainties inherent in their analysis.

Cost-Benefit Analysis↗